1. Field of the Invention
This invention relates to an internal combustion engine provided with an auxiliary combustion chamber in addition to a main combustion chamber, and more particularly to an engine having an auxiliary combustion chamber and a gasoline injection nozzle for use in a motor vehicle, which engine is designed to improve fuel consumption and purification of exhaust gases.
2. Description of the Prior Art
Hitherto, for stratifying a fuel-air mixture charge in a gasoline internal combustion engine, it is a common practice to inject the fuel into a single combustion chamber or to provide main and auxiliary combustion chambers and to separately supply the fuel therein through two fuel supply systems.
According to the former system, i.e., a single combustion chamber system, in which fuel is to be injected, a swirl flow of fuel-air mixture is developed within a cylinder volume by means of a shroud valve or a piston with a cup to achieve a stratified charge of the mixture. However, the former system is confronted by a difficulty in achieving a strong swirl throughout the entire operational modes consistently.
In contrast thereto, according to the latter system, i.e., in an engine having an auxiliary combustion chamber, fuel is injected into the auxiliary combustion chamber located separately from the main combustion chamber, in which a rich mixture charge is supplied to the auxiliary combustion chamber as well as a lean mixture to the main combustion chamber due to the escaping of part of fuel through the auxiliary combustion chamber into the main combustion chamber or to other fuel supplying system, so that the so-called stratified charges of fuel-air mixture may be achieved for two-stage combustions. In this case, the production of NOx of detrimental components contained in exhaust gases may be suppressed. However, because of the rich mixture charge in the auxiliary combustion chamber, there would be a tendency of increasing unfavorable amounts of emissions such as hydrocarbons and carbon monoxide.
For achieving stratification of the mixture charge in a gasoline engine having a carburetor, the fuel supply system should be divided into two systems one of which is to accommodate the supply of a rich mixture charge having good ignitability and the other of which is to supply a great amount of lean mixture charge which is burnt due to a flame injected through the passage from the auxiliary combustion chamber. In this case, for insuring the achievement of a rich mixture charge there has been proposed a small sized auxiliary valve for introducing the rich mixture into the auxiliary combustion chamber. However, this complicates the fuel supply system as well as the valve system. The reduction in volume of the auxiliary combustion chamber results in the similarity in construction to conventional engines having a carburetor, so that difficulties will be experienced with engine running when using a lean mixture charge. In general, for reducing the amount of NOx in exhaust gases from a gasoline engine with a carburetor, i.e., it is imperative to use an over-rich or over-lean mixture charge. Further in general, the gasoline engine with a carburetor dictates the use of the air-fuel ratio range of 11 to 20 for its satisfactory running. Thus, the use of over-rich mixture charge results in the increase of HC and CO together with the increase in fuel consumption, while the use of over-lean mixture charge leads to the occurrence of mis-fire, thus resulting in the increase in the amount of HC in exhaust gases.
With the stratified charge type combustion process, as used in the internal combustion engine according to the present invention, the combustion chamber is divided into a main combustion chamber and an auxiliary combustion chamber, wherein the main combustion chamber is communicated through a communicating passage with the auxiliary combustion chamber. In addition, the auxiliary combustion chamber is provided with an ignition plug, a fuel injection valve or a fuel injection nozzle, whereby the rich mixture charge is ignited in the auxiliary combustion chamber and then the flame thus produced is introduced into the main combustion chamber for the ensuing combustion of the lean mixture charge therein. In this case, air is supplied through the main combustion chamber into the auxiliary combustion chamber for stratification of mixture charge, with a minimum adverse affect by the throttling action due to the passage, and the flame is uniformly diffused throughout the main combustion chamber to effect the secondary combustion therein.